Stephen King's 1986 novel It is unusually long, clocking in at 1,138 pages for its original hardcover release. That necessitated significant changes when it was adapted to the screen. Chief among them was the book's regular use of flashbacks, periodically shifting between the childhoods of his misfit heroes in the late 1950s and their adult lives 27 years later. The book's popularity saw it adapted into a 1990 TV miniseries and a 2017/2019 movie duology, with the titular entity portrayed by Tim Curry and Bill Skarsgård in the corresponding version. The second adaptation of It switched things up by dividing each era in two and effectively shooting them as separate films.
Source：https://www.cbr.com/stephen-king-it-controversial-losers-club-scene-unadaptable/
